Semester 1 in Summary

3 weeks down, 3 to go. Here's a summary of physics so far:

Unit 1 - Units, Measurements, Relationships and Analysis

 Graphs with relationships such as linear, no relationship, inverse, exponential, and square root. Unit one covered how to do basic conversions between units, and how to decipher graphs. We also went over some definitions like

Precision: the consistency of measurements

Accuracy: The closeness of a measurement to the correct value

Independent variable: unaffected by other variables

Dependent variable: affected by the independent variable

Unit 2 - Kinematics - The Study of Motion

Scalar: a quantity that has magnitude

Vector: a quantity that has magnitude and direction

Acceleration: average velocity/time

All motion is relative!

d=1/2at^2+Vit

V=Vi+at

V^2=Vi^2+2ad

Unit 3 - Acceleration

Graphing rules:

-the slope of a position vs time graph is velocity

-the slope of a velocity vs time graph is acceleration

-the area under the "curve" of a velocity vs time graph is displacement 

Word Problem answer format:

-rewrite the question

-write down givens DATVVi

-make a sketch, include axes

-choose which equation

-plug n' chug

-box answer

-check!

Unit 4 - Projectile Motion

What happens in Vegas the axes, stay in Vegas the axes.

Always remember that the axes are independent! 

Parabolic motion: when an object is at the same level, moving at the same velocity 

Unit 5 - Forces in Equilibrium

And now for trig...

-SOHCAHTOA-

Vectors are equivalent if they have the same magnitude and direction. 

Pythagorean Therom: a^2+b^2=c^2

Bureku Technique

-Break up all diagonals (because we hate them) into x and y

-add all the values together, remembering that axes are independent

-UKERUB (put them together)

Force: a push or pull, vector quantity.

equilibrium: balanced

Normal force: supporting force that is perpendicular to the surface an object is on

Newton's Laws:

1. Inertia

Object in motion/at rest will tend to stay in motion/at rest unless acted upon by an unbalanced, outside force

2. Acceleration

The acceleration of an object is directly proportional to the net force of the object and inversely proportional to an objects mass (Fnet=ma)

3. Action&Reaction

The every force, there is an equal and opposite force. Equal in magnitude, opposite in direction.

A few things that I found enjoyable about physics so far would be the review sessions we have with the remotes. I find that's a really good way for me to contribute to class without necessarily having to talk much.

One challenge for me in physics would be staying awake during class. (Sorry Mr. Blake. No insult to your teaching abilities, just commentary on my inability to wake up early.)

Unit 6 - Forces that Accelerate

Today we started on Unit 6, and forces that accelerate. We spent a lot of time discussing one type of problem in particular, involving elevators. When elevators move at constant velocity, they have an acceleration of zero, like any other object moving at a constant velocity. But when it does accelerate, the acceleration is directly related to the net force on the elevator, which includes the weight of the elevator, a force going down, and the tension cable pulling the elevator up. However, elevators aren't always accelerating. They mostly accelerate at the beginning and the end of their journey, with a constant velocity in between.

If there's a person inside the elevator, as there often in, then the forces that are affecting them would be their weight and the normal force of the elevator floor beneath them. When the elevator is either moving at a constant velocity or at rest, the net force on the person would be zero. When the elevator is accelerating, the person is no longer in equilibrium, and either has a greater normal force or force of gravity acting upon them, causing them to feel either heavier or lighter depending on which direction the elevator is heading.

Here's a picture of some of my notes from today's discussion:

They're a little bit of a mess, because let's be honest, my understanding of this is sketchy at best.

Unit 5 - Friction

Growing up, I learned all my science lessons from Bill Nye. But this is one video in particular I remember watching on a couple different occasions, when there were substitute teachers who didn't know what else to do with us than have us watch educational videos. Here's 22 minutes worth of Bill Nye teaching you about friction.

In class today, we had an extremely education Slip n' Slide (doesn't it sound physics related?). When Gio first attempted to slide down it, there was only the plastic sheeting on the grass, no water or soap. Unfortunately, he didn't travel far. But when water was added, the friction decreased, increasing the distance traveled by our Slip n' Sliders. And eventually, with soap, the distance was increased so much so that people were able to travel to complete distance of the runway.

Newton's First Law

Today we started learning about different kinds of forces, and Newton's first law of motion.

Force can be defined as a push or pull, and an example of a "normal" force would be gravity, or your weight. You are constantly being pushed down by gravity, but it's being balanced by the force of the ground beneath your feet, keeping you in equilibrium. Normal force is defined as a supporting force that is perpendicular to the surface the object (in this case, you) are on.

Newton's first law of motion is the law of inertia.

-Objects in motion will tend to stay in motion, unless acted upon by an outside, unbalanced force.

-Objects at rest will tend to stay at rest, unless acted upon by an outside, unbalanced force.

The photo above is an example of this law. When you pull the paper out from under the pen, if you do it fast enough, the pen will stay still because it wants to stay inert.

The lab we did on Thursday was really good preparation for launching rockets. It was basically the same lab on a bigger scale, with rockets instead of balls, and shooting vertically into the air instead of horizontally. However, unlike the lab on Thursday, our predictions were not NEARLY as close. When we switched from shooting vertically into the air to shooting at an angle, towards Mr. Blake, our calculations were pretty off... Instead of the 54 something meters we were hoping it would fly, it only got about 15. It seems to be the proof I was waiting for that Unit 4 will be much more difficult than Unit 3. Kinematics in 3D instead of 2D means more math, more equations, and more ways to screw up.

Unit 4 - Projectile Motion

The lab we did today involved shooting a ball out of a projectile launcher. We used DAT, VAT, and VAD equations in order to figure out the muzzle velocity of the projectile launcher. From there, we were able to predict where the ball would land from different heights. Despite my initial apprehension at this assignment, the calculations came easier to me than I thought they would! This unit has made kinematics even more complicated, but so far, so good. Even though my group had a percent error of %3.125, I was still surprised by how close we ended up being to our predicted landing site.

1st Quarter Review

In the middle of our second week of class, the first quarter comes to close. So here's a quick recap of what we've learned so far:

Unit 1 - sort of a reintroduction to science courses, we went over conversions and the difference between accuracy and precision. Also an introduction to graphing, independent and dependent variables, and graph relationships (ex: linear, direct, inverse, exponential, square root).

Unit 2: Kinematics
Kinematics - The study of motion
We learned that you should always counter the question "is it moving?" with another question, "relative to what?'
Scalar vs Vector - scalar being a quantity that has magnitude, and vector being a quantity that has both magnitude and direction.

Unit 3: More Kinematics!
Equations were introduced to the Equation Board Not Bored in this lesson, such as DAT, VAT, and VAD. We also did a lot more work with graphs, like interpreting distance vs time, velocity vs time, and acceleration vs time.

Extra Credit

This is a video of me explaining to my mom the acceleration and velocity of an object thrown in the air. note - I said the acceleration was 9.2 m/s^2 instead of 9.8 by accident!

 The three graphs above all represent the same action, throwing a ball up and catching it above a motion sensor.  The red line is a Position vs Time graph, the green is Velocity vs Time, and the blue is Acceleration vs Time. They all have the same "fast, slow, stop, slow, fast" motion to them, just shown in different graphs and lines. As the ball is released when you toss it up, it’s moving at the fastest velocity. As it continues upwards, it begins to slow down, before reaching it’s stopping and highest point. When it begins it’s descent, it starts off slower and gets faster again as you catch it. The blue line is horizontal because it represents the acceleration, which is steady throughout because the acceleration is always based off of gravity, which is 9.8 m/s on planet Earth.

The seven step process of answering a word problem about acceleration and velocity goes like this:
1) Write the question, specifically what you need to find. So you can make the question more concise, only writing exactly what you need to find.
2)Write down your givens in order of d, a, t, v, initial v
3) Make a sketch to help your understanding of the problem, and be sure to include a set of axes.
4) Choose the correct equation, either dat, vat, or vad.
5)"plug&chug" plug in your values and get your answer!
6) Box your answer
7) Check to make sure your answer is logical

Here's an example:

Unit 2 - Is that moving?

Relative to what?

In Unit 2, we learned about how everything is always in motion, but it depends on what it's relative to. For instance, a outer part of a fan is not in motion in relation to the ground, but it is moving in relation to space. The blades of a fan, when it's turned on, are moving both in relation to the ground and in relation to space. (try and tilt your head. I have no idea how to rotate pictures on this).

 

We also learned about vectors, which I had learned a little bit about previously in the last cycle or two of Geometry. And I always, without fail, say it in Jason Segal's voice from Despicable Me. Something new that we discussed in class was scalar quantities, which is a quantity that has magnitude, or muchness. Vector quantities are similar, but along with magnitude they also have direction. Scalar quantities are things like distance or speed, and an example of a vector quantity is displacement, or the distance between where you are now and where you started. 

Unit 1

This graph shows the relationship between how much you eat and how hungry you are. It's an inverse relationship, because the more you eat, the less hungry you become. For example, if you eat 1/5 of your plate, you're still pretty hungry. If you continue to eat, say to 4/5 of your plate, you're now less hungry.

This graph depicts a direct relationship, because the more you sleep the more awake you are the next day. More sleep means more energy the next day! as the independent variable increases (the hours spent sleeping) so does the dependent variable (energy levels the next day.)


A squared relationship, like in this graph, shows how the y value is proportional to the square of the x value.


A square root relationship is just like a squared relationship, except in this case the y value is squared and the x value is not. The x and y values are still proportional.

This graph shows a linear relationship. A linear relationship shows that the independent variable has no affect on the dependent variable. Even as the x value increases, the y values stays the same.